Reapply "Isolated task support in Endpoints API: client side (3/3)" and fixes"

Reapply "Isolated task support in Endpoints API: client side (3/3)" and fixes"

Additional fixes:

- Fix shard pending when deduped and decorated.
- swarming.py bots was broken.
- Updated examples to exercise more code paths.
- Removed support for "auto-upload isolated file" in swarming.py trigger.
- Renamed Linux to Ubuntu in examples, as Linux is on its way out.

R=vadimsh@chromium.org
BUG=https://github.com/luci/luci-py/issues/197

Committed: https://github.com/luci/luci-py/commit/d03653b1439f6319b1a37cc9a46adfc2783d7c12

[M-A Ruel, 2015-09-14 15:50:30]

Patchset #2 (id:20001) has been deleted

[M-A Ruel, 2015-09-14 15:51:20]

Patchset #1 and #2 is the delta since the last try. It's quite large (sorry
about that) but I tested more code paths and more importantly switched to
namedtuple which standardized the API a bit, albeit not as clean as using a real
protobuf generated file.

[Vadim Sh., 2015-09-14 17:46:52]

lgtm with nit

https://codereview.chromium.org/1337633002/diff/40001/client/swarming.py
File client/swarming.py (right):

https://codereview.chromium.org/1337633002/diff/40001/client/swarming.py#newc...
client/swarming.py:226: env.append({'key': 'GTEST_SHARD_INDEX', 'value':
str(index)})
nit: override existing GTEST_SHARD_INDEX and GTEST_TOTAL_SHARDS

[M-A Ruel, 2015-09-15 14:13:38]

Patchset #3 (id:60001) has been deleted

[M-A Ruel, 2015-09-15 14:13:54]

https://codereview.chromium.org/1337633002/diff/40001/client/swarming.py
File client/swarming.py (right):

https://codereview.chromium.org/1337633002/diff/40001/client/swarming.py#newc...
client/swarming.py:226: env.append({'key': 'GTEST_SHARD_INDEX', 'value':
str(index)})
On 2015/09/14 17:46:52, Vadim Sh. wrote:
> nit: override existing GTEST_SHARD_INDEX and GTEST_TOTAL_SHARDS

Added asserts that they are not present instead. I feel this is safer, as
silently overriding values would be even more confusing

[M-A Ruel, 2015-09-15 19:32:44]

The CQ bit was checked by maruel@chromium.org

[M-A Ruel, 2015-09-15 19:32:45]

The patchset sent to the CQ was uploaded after l-g-t-m from vadimsh@chromium.org
Link to the patchset: https://codereview.chromium.org/1337633002/#ps80001
(title: "Final fixes")

[commit-bot: I haz the power, 2015-09-15 19:33:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1337633002/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1337633002/80001

[commit-bot: I haz the power, 2015-09-15 19:35:25]

Committed patchset #3 (id:80001) as
https://github.com/luci/luci-py/commit/d03653b1439f6319b1a37cc9a46adfc2783d7c12